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A133376 a(n) = (...((2^3)^4)^...)^n. 0

%I

%S 2,8,4096,1152921504606846976,

%T 2348542582773833227889480596789337027375682548908319870707290971532209025114608443463698998384768703031934976

%N a(n) = (...((2^3)^4)^...)^n.

%C Another kind of exponential factorial.

%C See cross-references for other possible definitions of exponential factorials.

%C Some other terms of the sequence can be computed, but they are quite large and it wouldn't be very convenient to display them.

%C The next term has 759 digits. - _Harvey P. Dale_, Oct 22 2019

%F a(n) = 2^(n!/2) for n >= 2. - _Karl W. Heuer_, Nov 25 2014

%e a(4) = 4096, as (2^3)^4 = 4096.

%p expfact:= proc(n::integer) local i,res; res:=2; for i from 3 to n do res:=(res)^i od; res end proc; seq(expfact(n), n=2..7);

%t nxt[{n_,a_}]:={n+1,a^(n+1)}; NestList[nxt,{2,2},4][[All,2]] (* _Harvey P. Dale_, Oct 22 2019 *)

%Y Cf. A124075, A049384.

%K nonn

%O 2,1

%A Pierre Karpman (pierre.karpman(AT)laposte.net), Oct 28 2007

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Last modified June 14 16:56 EDT 2021. Contains 345037 sequences. (Running on oeis4.)